A DC motor-driven fan is a relatively simple and well-known mechanism used to circulate air. In common applications, the fan blows the air through a heat exchanger, such as a radiator, condenser or evaporator. The air that flows through the heat exchanger may be used as a source of heating or cooling, for example in a car's heating, ventilation and air conditioning (HVAC) system or in regulating the temperature of a car's engine, motor, or battery pack. Unfortunately, when the heat exchanger becomes blocked, for example by debris and other contaminants, air cannot flow efficiently through the heat exchanger. As a result, the components and subsystems utilizing the heat exchanger may operate improperly and/or overheat and become damaged. Accordingly, what is needed is a system that allows the heat exchanger to be periodically checked to insure proper operation. The present invention provides such a system.